In the past, there have been many attempts to improve tennis rackets and other similar string rackets. For example, some rackets have been developed in which the longitudinal and transverse strings are in separate planes, rather than being interwoven in the conventional manner. In addition, in some of the rackets in which the longitudinal and transverse strings are in separate planes, the strings are bonded together at their crossing points rather than being interwoven so as to provide a faster method of stringing rackets, as exemplified in U.S. Pat. No. 3,834,699. Also, in order to decrease wear on the strings of rackets, friction-reducing members have been placed between the strings at their crossing points, as may be seen in U.S. Pat. Nos. 1,682,199 and 3,921,979. In addition to improving the structure and durability of tennis rackets, attempts have also been made to modify conventional tennis rackets so as to improve a player's performance. For example, in order to impart extra spin to a ball, the strings in the central playing area of a racket have been secured together at their crossings, such as shown in U.S. Pat. No. 1,531,778. However, present racket designs, including the numerous modifications which have been made thereto, do not substantially increase the amount of spin which can be imparted to a ball during play.
Accordingly, it is an object of the present invention to provide an improved game racket which substantially increases the amount of top spin, back spin, or side spin imparted to a ball during play. Specifically, it is within the contemplation of the present invention to provide an improved game racket which employs a unitary grid construction which operates so that the grid and the longitudinal or transverse strings of the racket move as a unit when the grid is struck by a ball to increase the amount of spin imparted to the ball.
It is a further object of the present invention to provide a unitary grid for game rackets having protuberances or roughened surfaces formed thereon so as to increase the frictional engagement and increase the time span during which the grid members contact the ball to increase the amount of top spin, back spin, or side spin imparted thereto.
It is a still further object of the present invention to provide an improved game racket wherein the amount of top spin or side spin imparted to a ball may be adjusted by varying the amount of tension on the longitudinal or transverse strings of the racket.